1. Field of the Invention
This invention relates to traffic noise barrier walls. More specifically, this invention relates to panels for traffic noise barrier walls.
2. Description of the Related Art
Traffic noise barrier walls serve to shield otherwise quiet areas from noise caused by automotive, railway, aircraft, marine, or pedestrian traffic. A typical traffic noise barrier wall is from about 4 to 18 feet in height and runs continuously alongside a selected section of a roadway, railway, aircraft runway, waterway, parking lot, walkway, and the like. Such walls are typically constructed of acoustically absorptive or reflective panels supported by vertically mounted posts.
FIG. 1 depicts one common design of a traffic noise barrier wall, which is indicated at 10. In the traffic noise barrier wall of FIG. 1, each panel 12 is constructed of wood or concrete and is supported between an adjacent pair of vertically mounted posts 14, with the side edges 16 of the panel 12 being received within slots 18 disposed in the posts 14 in “drop-down” fashion. That is, the side edges 16 of each panel 12 are aligned with the slots 18 and the panel 12 is lowered between the posts 14 to secure the panel 12 between the posts 14. Examples of such noise barrier walls are found in U.S. Pat. Nos. 5,713,170 and 5,537,788, both issued to Elmore et al. Noise barrier walls of this type are suitably sturdy and effective in reducing highway noise. However, the support posts must be sized to support the substantial weight of the wood or concrete panels under various environmental loads (e.g., wind loads, earthquake loads, etc.). As a result, the support posts found in such noise barrier walls are large and expensive to manufacture. Moreover, if it becomes necessary to increase the height of the wall after the wall has been built, the addition of more concrete or wood panels to the existing post structure is often times impossible due to the inability of the posts to handle the increased load caused by the additional panels. Such an addition in height may be required, for example, as noise regulations become more stringent or as the amount of noise generated by the traffic increases. Therefore, to increase the height of such noise barrier walls, the existing posts must be replaced at great expense.
Yet another drawback to the use of wood or concrete panels in a traffic noise barrier wall is that they block the view of any roadside businesses or scenery from travelers on the roadway. To overcome this deficiency, wall systems employing transparent panels have been developed. For example, U.S. Pat. No. 4,214,411 issued to Pickett describes panels of transparent polycarbonate resin for use as an acoustical barrier wall along a highway. While such wall systems are effective in providing travelers with a view outside the roadway, they typically require unique mounting structures that do not lend themselves to retrofit into the posts commonly used in traffic noise barrier walls.